A new digital age has dawned for manufacturers, and many must update or migrate their outdated distributed control systems (DCS) to stay competitive and meet ever-changing consumer demands. Their legacy systems have served them well, but as technology evolves, change is inevitable.
In 1959, for instance, the computer revolution met the industrial revolution in the downstream oil sector when the first industrial control computer system was built at the Texaco Port Arthur, Texas, refinery. Several years later, most of the process control in the oil and gas industry was migrated from pneumatic control loops and relay logic to an ensemble of distributed control systems (DCSs) from different vendors.
At the time, these cutting-edge systems brought to bear high-value-added technologies like graphical operator displays and a higher level of data analysis software. New control strategies were implemented and tested, at significantly reduced engineering time, with quicker alarm response and diagnostics. DCS vendors guaranteed a long product lifecycle for these robust, original systems.
In fact, many vendors have consolidated their obsolete products over the years and/or discontinued them entirely. Manufacturers now also realize that a migration entails a high level of difficulty and delicacy. If a DCS is the “brain” of the facility, migration carries a degree of risk analogous to brain surgery.
With that huge amount of risk, why would anyone choose to migrate? The answer is two-fold:
1. To avoid the enormous cost and risk associated with losing control of your processes
2. To utilize new innovative technologies to help improve operational efficiency and performance
Even knowing they need to take this migration path to stay competitive, manufacturers have a lot of uncertainty and doubt moving forward, especially where lack of resource bandwidth is an issue. A migration requires a huge amount of work. Risk can run high without the right team of experts to plan and implement the project. To this end, consider some of the associated risks inherent to a migration and how modernization can help overcome these hurdles.
Hardware obsolescence is the main driver for migrations in industry today. If equipment fails, the risk associated with unplanned downtime can be enormous—both from a safety and a
financial perspective. Safety instrumented systems (SISs) are designed to avoid a complete crisis, especially if the DCS fails. However, these systems are rarely tested in a way that could shut down an entire unit, such as a redundant controller failure event, where actuators attempt to revert to their failsafe mode of operation.
Beyond the inherent safety issue, when a continuous process stops being continuous, it is no longer profitable. Downtime outside of preplanned outages and turnarounds is extremely costly. Older DCS equipment, while built well, has a finite shelf life and will break at some point. Many legacy DCS parts are increasingly becoming unsupported with fewer replacement parts available. If manufacturers must acquire spare parts, they end up having to purchase more expensive and less reliable parts—the dreaded “eBay and pray.”
At a certain point—which is now for many facilities—the cost of maintaining systems exceeds the cost of an upgrade or migration. A major financial driver for performing an upgrade or migration is the increasing lack of knowledge and service support for legacy hardware and software. Over the years, many control engineers and technicians with legacy DCS experience have moved on from technical roles or are nearly at retirement age. With very little OEM support and training, this poses a problem both looking at the current system but also looking forward to future additions to the system. Filling this knowledge gap can be extremely difficult and costly as the demand and salary rate increases for experienced and knowledgeable engineers who understand these systems.
Another area to consider when replacing legacy equipment is cybersecurity vulnerabilities. Legacy systems were designed at a different time under the assumption that the “air gap” would protect the system from external, remote threats. However, many techniques have been developed to connect the process control system world to the business world. New technology and tools can be used to secure, manage, version, analyze, track and report automation-related process information and data. However, now that the “air gap” has been bridged, legacy systems are ripe for exploitation and represent a huge risk to any facility.
Today’s technologies provide significant opportunity to improve asset utilization and fully realize the benefits of big data, increased processing power and enhanced connectivity. Many legacy control systems rely on proprietary data structures that lack interoperability between systems. Increasingly, manufacturers look to utilize this data for various functions—analytics, environmental calculations and monitoring, integration into enterprise resource planning (ERP), asset management, predictive maintenance, digital twins and various other industrial internet of things (IIoT) applications. Modern control systems can deliver accurate real-time data reliably to enable these capabilities.
With increased process power, manufacturers can leverage more complex process control techniques. Legacy DCS platforms designed 30 or 40 years ago had constraints that are no longer valid. Process control techniques like initialization, windup protection, and override selection are no longer an issue and easily incorporated into control strategies. Model predictive control and fuzzy logic can be implemented without requiring additional software and licenses, allowing facilities to use software simulation (whether simple loopback or more dynamic methods) instead of testing on actual hardware. Offline configuration testing and operator training can then be conducted more easily, inexpensively, accurately, and safely than ever before.
Legacy control systems’ reliance on outdated user interfaces and unintuitive programming styles creates a situation that increases implementation time and therefore costs, creating an obstructive barrier for new engineers or technicians to grasp. Maintaining and manipulating large databases using Excel or XML formats versus older text dumps allows for increased quality control and the ability to build and edit large amounts of programming in bulk.
Graphical function block configuration is a common feature in modern control systems and is significantly easier to learn, maintain, and document than the older, text-based forms. Sequential logic programming and troubleshooting is also much easier. Homing in on the exact stuck valve is significantly quicker than looking at a valve lineup and trying to make sense of poorly commented 20-year-old structured text program. It’s also possible to improve the operator human-machine interface (HMI) and incorporate high-performance graphics for optimal operator awareness and alarm response, increasing safety.
A migration offers the ability to have a well-documented system. Multiple generations of workers have added on to these systems, utilizing different standards. They most likely have abandoned logic muddying the system. A migration presents a “once-in-a-career” opportunity to start with a clean slate and correct past bad habits and inconsistencies.
How to Modernize
A complex effort like a DCS migration requires a planned, thoughtful approach. When one failed project can create such enormous cost increases, mitigating risk is paramount. If done right, a migration project should only happen once in a career, so it shouldn’t be taken lightly. Before starting, consider the following factors to position a migration for success.
Domain and business expertise must come to the forefront before starting a migration. You wouldn’t hire an electrician to do your plumbing, so why would you trust someone who has never done DCS migrations to execute them? Each process unit has different inputs, equipment, operating conditions, safety risks, and peculiarities that may not be obvious to someone without that experience. If lack of resource bandwidth is a concern, consider consulting a platform-independent third-party partner, who has experience in legacy systems and modernization tools and techniques.
Planning and Budgeting Phase
Emphasis should be placed on the planning and budgeting phase via a front-end loading (FEL) process. An FEL approach helps reduce overall operational project costs, minimizes scheduling issues, decreases scope changes after authorization, and increases likelihood that a project meets or exceeds financial goal. This way avoids accidents and downtime, especially considering how intertwined process units are, with products and byproducts from different units being fed and reprocessed throughout the facility. Ideally, for example, cutting over a control system should occur while the unit is down for maintenance. Some ancillary units may be able to be cutover during partial turnarounds or equipment inspections, while others only come down for full facility shutdowns (which may only occur every couple of years). Understanding each process unit’s maintenance schedule and interactions with other process units is key to an efficient FEL migration plan.
The commercial side is similar. A facility’s goal is to generate revenue and profit. A DCS migration should protect and enhance that ability. Having a clear idea about how much the effort will cost and the allotted time needed to justify and incorporate it into the capital budget is key to getting enterprise-wide buy-in. The FEL planning stage should accurately determine the effort and time required for the migration. For instance, it should include the estimates to reverse-engineer and document the old system and to engineer and test the new system. It should also include the installation, electrical, hardware, and software costs for the actual DCS. All discovery and documents must be continually modified and refined as the project progresses, which will result in an overall project cost savings and lower risk. Again, an experienced third-party automation team can help with proper, upfront FEL planning to avoid risk and lower your costs.
System and Vendor Selection
A large part of any DCS migration is choosing a new system. A wrong decision can result in millions of lost dollars and countless years of frustrated engineers, operators, and procurement (too often an iteration of the slogan, “you’ll never pay more for less” comes up). The selection process typically comes down to one of two decisions, each with its pros and cons: 1) Stick with the same vendor, if possible, or 2) switch.
Sticking with the same vendor can be a positive in that they typically have a well-defined path to help you plan and execute the migration. Another benefit is that many of the control strategies may be ported much more easily with several of the control features having similar functionality as the legacy control system—which may not be the case with a new vendor. A risk to consider for both paths during the FEL planning stages is that many of these vendors have a conflict of interest with their customers to sell additional hardware and software that may not be necessary or best practice. A large issue that arises during actual execution is DCS vendors oftentimes largely rely on automated tools that may capture the original code without a high degree of accuracy. Correcting this code manually can be a huge undertaking.
During the typical “dog and pony show,” each vendor is predisposed to flaunting their “best-in-class” product and solution for every application, making it extremely difficult to discern the right decision. To truly make an informed, unbiased decision, a facility should specify critical to quality (CTQ) parameters by working with key stakeholders—operators, process engineers, maintenance, production management, and others. These parameters should include considerations like advanced process control (APC) support, scalability, life support track record, high-performance graphics, migration path, industry and region install base, IIoT, and control strategy portability. Here, consulting an unbiased third-party partner with experience in all these vendors and technologies helps provide a holistic view of how these vendors stack in each of these CTQs and allows for the best possible decision.
Change is painful. Modernizing a control system is a huge, risky, but highly necessary, undertaking. Taking a proactive and planned approach allows for the required steps to be taken to mitigate this risk and migrate the system accurately, safely, and more cost effectively. The improved functionality and profitability gained by utilizing a modern, newly optimized control system will make it so that your engineers, technicians, facility managers, procurement, and even investors will thank you.
Stout, T. M.; Williams, T. J. (1995). “Pioneering Work in the Field of Computer Process Control.” IEEE Annals of the History of Computing.